NASA/TM--2003-212086

Realistic Subscale Evaluations of the

Mechanical Properties of Advanced

Disk Superalloys

Timothy R Gabb, John Gayda, and Jack Telesman

Glenn Research Center, Cleveland, Ohio

Peter T. Kantzos

Ohio Aerospace Institute, Brook Park, Ohio

William A. Konkel

Konkel Material Consulting, Bellaire, Texas

January 2003
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NASA/TM--2003-212086

Realistic Subscale Evaluations of the

Mechanical Properties of Advanced

Disk Superalloys

Timothy R Gabb, John Gayda, and Jack Telesman

Glenn Research Center, Cleveland, Ohio

Peter T. Kantzos

Ohio Aerospace Institute, Brook Park, Ohio

William A. Konkel

Konkel Material Consulting, Bellaire, Texas

Prepared for the

2003 Annual Meeting and Exhibition

sponsored by The Minerals, Metals, and Materials Society

San Diego, California, March 2-6, 2003

National Aeronautics and

Space Administration

Glenn Research Center

January 2003
Acknowledgments

The authors wish to acknowledge Tony Banik of Special Metals Corporation, for experimental alloy powder

processing. Gil London and Rob Kwalik of Naval Air Warfare Center, Rick Montero of Pratt & Whitney Engine

Company, and Kenneth Bain of General Electric Aircraft Engines are also acknowledged for providing powder for

one allo}a This work was performed in support of the NASA HOTPC, Ultrasafe, and UEET programs.

The Aerospace Propulsion and Power Program at

NASA Glenn Research Center sponsored this work.

NASA Center for Aerospace Information

7121 Standard Drive

Hanover, MD 21076

Available from

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22100

Available electronically at http://gltrs.grc.nasa.gov
REALISTIC SUBSCALE EVALUATIONS OF THE MECHANICAL PROPERTIES OF

ADVANCED DISK SUPERALLOYS

T.P. Gabb, 1 J. Gayda, 1 J. Telesman, 1 P.T. Kantzos, 2 and W.A. Konkel 3

1NASA Glenn Research Center, 21000 Brookpark Rd., Cleveland, OH 44135

2Ohio Aerospace Institute, 22800 Cedar Point Road, Brook Park, OH 44142

3Konkel Material Consulting, 4605 Holly Dr., Bellaire, TX 77410

Abstract

A series of experimental powder metallurgy disk alloys were evaluated for their processing

characteristics and high temperature mechanical properties. Powder of each alloy was hot

compacted, extruded, and isothermally forged into subscale disks. Disks were subsolvus and

supersolvus heat treated, then quenched using procedures designed to reproduce the cooling

paths expected in large-scale disks. Mechanical tests were then performed at 538, 704, and

815 °C. Several alloys had superior tensile and creep properties at 704 °C and higher

temperatures, but were difficult to process and prone to quench cracking, chiefly due to their

high gamma prime solvus temperature. Several other alloys had more favorable processing

characteristics due to their lower gamma prime solvus temperature and balanced timedependent properties at 704 °C. Results indicate an experimental low solvus, high refractory

alloy can build upon the best attributes of all these alloys, giving exceptional tensile and creep

properties at high temperatures with good processing characteristics due to a low gamma prime

solvus.

Introduction

Advanced powder metallurgy disk alloys such as ME3 and Alloy 10 were designed using

divergent screening and optimization approaches for composition and processing variables in

several cooperative government-industry programs. ME3 was developed and scaled-up by the

team of NASA, General Electric, and Pratt & Whitney in the NASA High Speed

Research/Enabling Propulsion Materials (HSR/EPM) Compressor/Turbine Disk program to

have extended durability at 650 °C in large engine compressor and turbine disks [1]. Alloy 10

was developed by Honeywell Engine Systems to produce superior tensile, creep, and fatigue

resistance in smaller engine disks at temperatures above 650 °C [2].

There is a long-term need for disks with higher rim temperature capabilities of 704 °C or more.

This would allow higher compressor exit (T3) temperatures and allow the full utilization of

advanced combustor and airfoil concepts under development. The balance of mechanical

properties necessary to achieve these temperature capabilities could vary with engine size and

engine cycle design, as well as the particulars of a selected potential disk design and location in

an engine. Such detailed design assessments are beyond the scope of this study. However, a

brief screening characterization of the mechanical properties of experimental disk alloys at high

temperature would allow initial assessments of the balance of properties produced by modified

chemistries.

NASA/TM--2003-212086 1
Variationsin diskalloychemistrycanbeusedtohelpachievetheseimprovementsin

temperaturecapability.Thiscanbeassessedbyprocessingandtestingsubscaledisksmade

withintentionallyvariedexperimentaldiskalloypowderchemistries.However,avery

importantconsiderationin heattreatingsubscaledisksis thequenchingproceduresafter

solutionheattreatments.Smallsubscalediskshavinglow masstendto coolmuchfasterthan

large-scaledisksfor agivenquenchingprocedure.Thiscanproduceunrealisticmechanical

propertiesin thesubscalematerial,whichcannotbeeasilyattainedin largescaledisks.

Therefore,modifiedquenchingproceduresarenecessaryfor subscaledisks.

Theobjectiveof thisstudywasto developandperformrealisticquenchingheattreatmentson

subscaledisksof severaladvancedpowdermetallurgydisk superalloys.Therealistic

quenchingheattreatmentswerefirstdevelopedandverifiedto givein subscaledisks

comparablemechanicalpropertiesto largescaledisks.Thehightemperaturemechanical

propertiesof experimentalsuperalloyswerethenscreenedin searchof analloyhavinghigh

temperaturecapability.

Materials and Procedure

A series of experimental advanced powder metallurgy disk alloys were evaluated for their

processing characteristics and high temperature mechanical properties. The overall variations

of composition in weight percent among these alloys were 3.3-4.0 A1, 0.024-.030 B, 0.028-.050

C, 15.2-20.7 Co, 9.5-13.3 Cr, 2.5-3.7 Mo, 0-1.9 Nb, 1.0-2.6 Ta, 3.3-3.8 Ti, 2.1-5.9 W, 0.05-0.1

Zr, and balance Ni. Powder of each superalloy was hot compacted and extruded. Extrusion

segments of the superalloys were machined to mults 7 to 8 cm dia. and 15 to 16 cm long, then

forged into subscale disks about 13 to 14 cm in diameter and 4 cm thick by Wyman-Gordon

Forgings. They were then heat treated using several procedures.

Mechanical test conditions of subscale disks after heat treatments were selected to screen high

temperature properties and allow limited direct comparisons with specimen tests from the scaleup disks.

Tensile Tests

Tests of subscale material were performed at Dickson Testing Company and NASA GRC on

specimens machined by Metcut Research Associates having a gage diameter of 0.41 cm and

gage length of 2.5 cm in a uniaxial test machine employing a resistance heating furnace and

axial extensometer according to ASTM E21.

Creep Tests

Machining of subscale disk creep specimens was performed by Metcut Research Associates.

Specimens having a gage diameter of 0.64 cm and gage length of 3.8 cm were machined and

tested in uniaxial lever arm constant load creep frames using resistance heating furnaces and

shoulder-mounted extensometers. The creep tests were performed by NASA GRC and Metcut

Research Associates according to ASTM E139.

Fatigue Crack Growth Tests

Machining of surface flaw fatigue crack growth specimens from subscale disks was performed

by BITEC CNC Machining. All specimens had a rectangular gage section 1 cm wide and

NASA/TM--2003-212086 2
0.46 cm thick, with a surface flaw about 0.036 cm wide and 0.018 cm deep produced by

electro-discharge machining. The fatigue crack growth specimens were then tested at NASA

GRC. Tests were performed in a closed-loop servohydraulic test machine using resistance

heating and potential drop measurement of crack growth. Pre-cracking was performed at room

temperature. Tests were then performed at elevated temperatures using a maximum stress of

690 MPa. Cyclic dwell tests were performed at 704 °C with a 90 s dwell at maximum stress,

using a stress ratio of 0.05.

Grain sizes were determined according to ASTM E112 linear intercept procedures using

circular grid overlays.

Results and Discussion

Heat Treatments and Microstructure Response

Grain size as a function of solution heat treatment temperature was first screened for all alloys

using small coupons. Grain size increased nonlinearly with temperature as shown in Fig. 1. At

low solution temperatures the grain size was relatively stable at ASTM 12-11 (5 to 10 _tm).

Increasing temperature to a certain level produced a sharp step increase in grain size to ASTM

7-6 (40 to 55 _tm). This was due to the dissolving of most of the prior existing coarse

"primary" 7" precipitates which constrain grain growth. The temperature producing a

transitioning grain size of ASTM 9.5 (13 _tm) within the step increase was selected to define a

practical "solvus" temperature of the alloy which dissolved enough of the "primary" 7"

precipitates (90 to 95 percent) to allow the grain growth. The solvus temperature producing this

sharp increase in grain size varied among the alloys. ME3 and a group of experimental °'LS"

series alloys had low solvus temperatures of 1150 to 1160 °C. Alloy 10 and a group of

experimental "HS" series alloys had high solvus temperatures of 1170 to 1190 °C.

It was intended that the subscale disks be quenched from the solution heat treatments at cooling

rates typically expected at near-surface to deeply imbedded locations of large scale disks of one

to several hundred pounds weight which were oil quenched. Due to the much lower weight and

volume of the subscale disks, this required design and screening of slower cooling procedures

than typically employed for large disks. A procedure of fan air cooling starting 2 minutes after

13.0

12.0

11.0

oo

.E 10.0

(_9 9.0

iI

oo 8.0

0

o:

0

G

[]

0

• ME3 8 o

o LS Series _ _ o t

o HS Series + o

°

7.0 - IAIInvln -* • []

6.0 I

1120 1130 1140 1150 1160 1170 1180 1190 1200

Temperature-C

Figure 1 Grain size versus solution heat treatment temperature.

NASA/TM--2003-212086 3
removal from the furnace was adopted to simulate deeply imbedded bore locations in large

disks. An additional disk of each alloy was directly oil quenched starting 3 0 seconds after

removal from the furnace, to simulate faster cooling rates near the surfaces of large disks. The

cooling temperature-time data of thermocouples embedded in the middle ("bore") and near the

comer ("rim") of a subscale disk are compared in Fig. 2. The temperature-time paths of cooling

measured in the subscale disks was similar to that expected for large disks. The thermocouple

temperature-time data recorded from 4 thermocouples embedded in one of the subscale disks

during fan air and oil quenching cycles was analyzed using a commercial heat transfer

computer code in order to assign approximate cooling rates, averaged over the temperature

range of solution temperature to 815 °C, for each specimen. All subscale disks were

subsequently given an aging heat treatment of 815 °C/8h.

The response to quenching varied among the alloys. All disks survived quenching from

subsolvus solution temperatures. However, several of the disks formed edge cracks of 1 to

8 cm length during quenching from supersolvus solution temperatures. The location and

intergranular mode of these quench cracks was comparable to that previously observed in large

scale disks, Fig. 3. Comparing among alloys, alloys having the high solvus temperatures and

corresponding supersolvus solution heat treatment temperatures had a propensity of cracking.

This has also been observed in preliminary repeated testing of tensile and coin-sized disk

specimens of Alloy 10 and ME3, respectively [3, 4]. Therefore, it will be important to consider

solvus temperature when comparing the resulting mechanical properties among the alloys.

0

__ -100

_- -200

I-

-3oo

_D

-400

+ Fan Air Quenched Bore

x Fan Air Quenched Rim

• Oil Quenched Bore

o Oil Quenched Rim

\\ ',,

0 1 2 3 4 5 6

Ti me-mi n.

Figure 2: Thermocouple temperature versus time at different locations in subscale disks.

l'Y 

(a) (b)

Figure 3: Quench cracks in high solvus alloy disks: (a) Subscale disk (b) Large scale disk.

NASA/TM--2003-212086 4
m

10 pm

(a) (b)

Figure 4: Typical microstructures: (a) Supersolvus solution heat treated, then oil quenched

(b) Supersolvus solution heat treated, fan air cooled.

Typical grain microstructures in optical images of etched metallographic sections of specimen

grip sections are shown in Fig. 4. These microstructures were from oil quenched and fan

cooled supersolvus heat treated disks. Supersolvus material heat treated at about 15 °C above

each alloy's solvus temperature had a mean ASTM grain size of 7.1 with a standard deviation

of 0.3, and an ALA ASTM grain size of 3.1 with a standard deviation of 0.4 for all alloys.

Serrated grain boundaries were usually observed for the slower cooled fan air quenched

material, while straighter grain boundaries were observed for the faster cooled oil quenched

material. Subsolvus material heat treated at about 25 °C below each alloy's solvus temperature

had a mean ASTM grain size of 12 with a standard deviation of 0.2, and an ALA ASTM grain

size of 7.4 with a standard deviation of 0.9 for all alloys.

Mechanical Properties

Subscale versus Large Scale Properties. ME3 tensile strengths and creep lives are compared

from specimen tests of the subscale disks and large contoured turbine disks over 60 cm in

diameter and 10 cm in maximum bore thickness in Fig. 5. The scatter in response observed at

each test condition for each disk could be attributed in part to variations in local cooling rate,

with higher cooling rates producing higher tensile strength and creep life [1, 5]. The mechanical

properties were quite comparable for the two disks, indicating the subscale heat treatments

could produce mechanical properties representative of large scale disk material.

Tensile Response. Ultimate strengths are compared as functions of solvus temperature among

all alloys for supersolvus and subsolvus heat treated subscale disks in Figs. 6 and 7. Strength

decreased with increasing temperature for both supersolvus and subsolvus heat treated material.

Supersolvus material had slightly lower strength than subsolvus material at 704 °C. Alloys

with higher solvus temperature had generally higher strengths than the lower solvus alloys. But

several lower solvus alloys had strengths approaching the higher solvus alloy levels.

Creep Properties. Times to 0.2 percent creep are compared as functions of solvus temperature

among all alloys for supersolvus and subsolvus heat treated subscale as functions of solvus

temperature disks in Figs. 8 and 9. Creep response of the coarse grain supersolvus material was

superior to that of the fine grain subsolvus material, due to grain size effects. The examined

alloys with higher solvus temperature had generally higher creep lives than the lower solvus

alloys. But several lower solvus alloys had lives approaching the higher solvus alloy levels.

NASA/TM--2003-212086 5
13_

_&

¢-

O9

1800 '

1600

1400 x

×

1200 _ []

N

|

X

1000 × Large Scale Disks []

800 [] Subscale Disks

500 600 700 800

Temperature-C

1000

8OO

a_ 600

09

400

O9

2OO

0

900 10

x Large Scale 650C

+ Large Scale 704C

[] Subscale 650C

o Subscale 704C

........ I ........ I ........

100 1000 10000

Life-h

(a) (b)

Figure 5: Supersolvus ME3 subscale versus large scale disk properties: (a) Tensile strength

(b) Creep life.

15OO

1400 _ [] [] _

[] []

I 1300 _ [] [] _c

e"- e"- 1200

O9 O9

1100 •ME3

E _ LS Series ._E

5 1000 [] HS Series D

• Alloy 10

900 1

1500 ...........

1400

1300

1200

1100

1000 7°

900 ,

• ME3

o LS Series

[] HS Series

• Alloy 10

[] II

[]

e [] []

1150 1160 1170 1180 1190 1150 1160 1170 1180 1190

Solvus-C Solvus-C

(a) (b)

Figure 6: Supersolvus subscale disk tensile strength for all alloys: (a) 704 °C (b) 815 °C.

NASA/TM--2003-212086 6
13_

1800_

1700

1600

o I I

o

1500 ---

1400

• ME3

. LS Series

[] HS Series

• Alloy 10

1300 i,, i,, i , ,

13_

1800

1700

1600

1500

1400

1300

1140 1160 1180 1200 1140 1160 1180 1200

Solvus-C Solvus-C

(a) (b)

Figure 7: Subsolvus disk tensile strength for all alloys: (a) 538 °C (b) 704 °C.

1000

E

100

o

O

10

1000

o

!' []

• ME3

° LS Series

[] HS Series

• Alloy 10

1160 1170 1180 1190

Solvus-C

i

._1

O..

100

o

o--e

(N

O

o

@ • ME3

o LS Series

[] HS Series

• Alloy 10

[]

!

i

10 , I , I ,

1150 1150 1160 1170 1180 1190

Solvus-C

(a) (b)

Figure 8: Supersolvus disk creep life for all alloys: (a) 704 °C/690 MPa

(b) 815 °C/345 MPa.

NASA/TM--2003-212086 7
..J

o

o-e

t'N

O

1000

100

° • ME3 •

o LS Series

. HS Series

• Alloy 10

10 I

1150 1160 1170 1180 1190

Solvus-C

Figure 9: Comparison ofsubsolvussubscale disk creepli_forallalloys

704 °C/690MPa.

1.0E-03

E

E

$ 1.0E-04

nt-"

O

1.0E-05

O

O

1.0E-06

o

1150 1160 1170 1180 1190

Solvus-C

Figure 10: Comparison of supersolvus subscale disk dwell crack growth rates for all alloys

at 25 MPa*m °5 in 704 °C/90 s dwell tests.

Fatigue Crack Growth Properties. Dwell crack growth rates at a maximum stress intensity of

25 MPa*m °5 are compared versus solvus temperature among all alloys for supersolvus heat

treated subscale disks in Fig. 10. No clear trends were observed with the solvus temperature of

the alloy. ME3, Alloy 10, and several LS and HS series alloys had sufficient resistance to

dwell crack growth.

Balance of Properties Among All Alloys. Alloys with higher solvus temperature generally had

higher strength and creep resistance than the lower solvus alloys. However, the highest strength

alloys were more difficult to process and prone to quench cracking, chiefly due to their high

solvus temperature. Alloys with lower solvus temperature had generally lower strength and

creep resistance, but were less prone to quench cracking. There was no clear trend of crack

growth resistance with alloy solvus temperature, strength, or creep resistance. Therefore, the

NASA/TM--2003-212086 8
(.3

_b

o

03

• ME3

<, LS Series

[] HS Series

• Alloy 10

11901

118C

117C

704C Propertiesvs. Solvus • ME3

o LS Series

HS Series

Alloy 10

815C Properties vs. Solvus

1500 116C

1150

1000

704C/690Mpa/0.2 % 100 1200

CreepLife_h

(a)

Figure 11: Balance of supersolvus tensile

1180

0

> 1170

1160

1150

1000 . ...... 1000 ._O

-4L.. og,-

815C/345Mp 1O0

a/02% Creep Life.h

(b)

creep, and solvus properties for all alloys:

(a) 704 °C (b) 815 °C.

• ME3

o LS Series

[] HS Series

• Alloy 10 i. " ......

iJi

o .- ......{--o_......... r i

1500 1160 -. ....... --. ;*. _,o ........ •_ _/. ...;.......___ ....../1450 .00

I ,,Z ; ....... _d ..... $1400 ,@

1150 __._ -: ........ _":\_ /1350 ,,_c-d

1000 _ ........ ZW/j3o0#

5°

"04C/6,gnA ,_ 1O0 ""-""'_ 1200 "

v°UMPa/02% Cr

eep Life.h

Figure 12: Balance of tensile, creep, and solvus properties for all subsolvus alloys.

most desirable alloy should have high strength and creep resistance combined with low solvus

temperature. The balance of strength, creep life, and solvus temperature is compared for the

supersolvus and subsolvus heat treated alloys in Figs. 11 and 12. Several LS series alloys did

have a favorable balance of improved tensile and creep response combined with low solvus

temperature. Among these, an optimal low solvus, high refractory (LSHR) alloy was identified

which combined the best attributes of all these alloys, giving exceptional tensile and creep

properties at high temperatures with good processing characteristics. The high refractory

element levels gave exceptional tensile and creep properties at high temperatures, while the

overall chemistry gave good processing characteristics including a low gamma prime solvus

and resistance to quench cracking. This LSHR alloy, having a nominal composition in weight

percent of 3.5 A1-0.03 B-0.03 C-20.7Co- 12.5 Cr-2.7Mo- 1.5Nb- 1.6Ta-3.5 Ti-4.3 W-0.05Zr-bal. Ni,

is now being scaled up for expanded processing and mechanical property assessments.

NASA/TM--2003-212086 9
Summary and Conclusions

A series of subscale experimental powder metallurgy disk alloys were evaluated for their

processing characteristics and high temperature mechanical properties. Heat treatment

procedures were developed which could reproduce in subscale disks the cooling paths and

mechanical properties of large scale disks. Several subscale alloys had superior tensile and

creep properties at 704 °C and higher temperatures, but were difficult to process and prone to

quench cracking, chiefly due to their high gamma prime solvus temperature. Several other

alloys had more favorable processing characteristics due to their lower gamma prime solvus

temperature. These alloys often had lower tensile and creep properties at high temperatures.

Several experimental low solvus, high property alloys were identified which could build upon

the best attributes of all these alloys, giving exceptional tensile and creep properties at high

temperatures along with good processing characteristics due to a low gamma prime solvus.

It can be concluded from this evaluation that:

(1) Subscale evaluations of disk alloys can be designed to realistically reproduce the

cooling paths and mechanical properties expected from large scale disks.

(2) New disk alloy chemistries can be used to improve mechanical properties at high

temperatures.

(3) Alloys having high solvus temperature are more prone to form cracks during quenching.

(4) An alloy can be designed to provide a low solvus temperature for ease in processing

with exceptional tensile and creep properties at high temperatures.

References

. T.P. Gabb, J. Telesman, P.T. Kantzos, and K. O'Connor, "Characterization of the

Temperature Capabilities of Advanced Disk Alloy ME3," NASA/TM--2002-211796,

Washington, D.C., 2002.

2. H. Merrick, R.C. Benn, and P.R. Bhowal, U.S. Patent 6,468,368, Washington, D.C., 2002.

. T.P. Gabb, J. Gayda, P.T. Kantzos, T. Biles, and W.A. Konkel, "The Tensile Properties of

Disk Superalloys During Supersolvus Quenching Heat Treatments," Materials Design

Approaches and Experiences, ed. J.-C. Zhao, M. Fahrmann, T.M. Pollock, TMS,

Warrendale, PA, 2001, pp. 267-279.

4. J. Gayda, P.T. Kantzos, and J. Miller, "Quench Crack Behavior of Nickel Base Disk

Superalloys," NASA/TM--2002-211984, Washington, D.C., 2002.

. J.R. Groh, "Effect of Cooling Rate From Solution Heat Treatment on Waspaloy

Microstructure and Properties," Superallovs 1996, ed. R.D. Kissinger, D.J. Deye, D.L.

Anton, A.D. Cetel, M.V. Nathal, T.M. Pollock, and D.A. Woodford, TMS, Warrendale,

PA, 1996, pp. 687-696.

NASA/TM--2003-212086 10
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January 2003 Technical Memorandum

4. TITLE AND SUBTITLE 5. FUNDING NUMBERS

Realistic Subscale Evaluations of the Mechanical Properties of Advanced

Disk Superalloys

6. AUTHOR(S)

Timothy R Gabb, John Gayda, Jack Telesman, Peter T. Kantzos, and

William A. Konkel

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

John H. Glenn Research Center at Lewis Field

Cleveland, Ohio 44135-3191

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Washington, DC 20546-0001

WB S-22-708-31-03

8. PERFORMING ORGANIZATION

REPORT NUMBER

E- 13739

10. SPONSORIN G/MONITORIN G

AGENCY REPORT NUMBER

NASA TM--2003-212086

11. SUPPLEMENTARY NOTES

Prepared for the 2003 Annual Meeting and Exhibition sponsored by The Minerals, Metals, and Materials Society,

San Diego, California, March 2-6, 2003. Timothy R Gabb, John Gayda, and Jack Telesman, NASA Glenn Research

Center; Peter T. Kantzos, Ohio Aerospace Institute, Brook Park, Ohio 44142; William A. Konkel, Konkel Material

Consulting, 4605 Holly Drive, Bellalre, Texas 77410. Responsible person, Timoth I R Gabb, organization code 5120,

216-433-3272.

12a. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified - Unlimited

Subject Category: 07 Distribution: Nonstandard

Available electronically at http://gltrs.grc.nasa.gov

This publication is available from the NASA Center for AeroSpace Information, 301-621-0390.

12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words)

A series of experimental powder metallurgy disk alloys were evaluated for their processing characteristics and high

temperature mechanical properties. Powder of each alloy was hot compacted, extruded, and isothermally forged into

subscale disks. Disks were subsolvus and supersolvus heat treated, then quenched using procedures designed to

reproduce the cooling paths expected in large-scale disks. Mechanical tests were then performed at 538, 704, and

815°C. Several alloys had superior tensile and creep properties at 704°C and higher temperatures, but were difficult to

process and prone to quench cracking, chiefly due to their high gamma prime solvus temperature. Several other alloys

had more favorable processing characteristics due to their lower gamma prime solvus temperature and balanced timedependent properties at 704°C. Results indicate an experimental low solvus, high refractory alloy can build upon the

best attributes of all these alloys, giving exceptional tensile and creep properties at high temperatures with good

processing characteristics due to a low gamma prime solvus.

14. SUBJECT TERMS

Heat treatment; Rotating disks; Creep properties; Tensile strength; Heat resistant alloy;

Superalloys

17. SECURITY CLASSIFICATION

OF REPORT

Unclassified

NSN 7540-01-280-5500

15. NUMBER OF PAGES

16

16. PRICE CODE

18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT

OF THIS PAGE OF ABSTRACT

Unclassified Unclassified

Standard Form 298 (Rev. 2-89)

Prescribed by ANSI Std. Z39-18

298-102